most of pagerank predates larry; several people were already looking at using centrality measures for page ranking before him. And I think Brin contributed a lot more of the math and theory than Page ever did.
Yeah, Sergey was better with numbers. Like that time when a PM was showing a new payment product on stage and he asked "was that your real credit card number?". She confirmed it was, to which he replied "Anyone could have memorized it... [starts reciting the digits, with the demo already at the next screen]".